Essential PHP Interview Questions for Experienced Developers

Essential PHP Interview Questions for Experienced Developers

PHP Interview Questions for Experienced

With this post, we have prepared the must-have list of PHP Interview Questions for Experienced developers.

PHP is still dominating the big market share in web application development. Experienced PHP developers are always in great demand for web development companies. In addition to our previous guide of PHP Interview Questions, we are providing another set of PHP Interview Questions for experienced developers.

This PHP Interview Questions for Experienced guide would help both organizations seeking expert PHP developers and candidates preparing for PHP developer interviews.

PHP Interview Questions for Experienced Developers

Q1). How to define a constant in PHP?

A constant in PHP is a variable whose value is fixed throughout the PHP program or script. Unlike variables, the value of the constant can not be modified at runtime when the PHP script is running.

The PHP define() function is used to define a constant.

PHP constant example

For example, Lets create SYNC_FREQUENCY as a constant:define(‘SYNC_FREQUENCY’, ’10’);

PHP Interview Questions for Experienced Developers.

Q2). What is the difference between PHP explode() and implode() functions?

Answer:

The PHP explode() function creates an array from a given string. The delimiter argument split the data argument into multiple elements. This function is safe to use with binary strings. The implode function will convert an array into a string.

The PHP implode() function is reverse of explode(). The PHP implode() functions is used to transform an array into a single string. The array elements are concatenated with the delimiter string separating them. To perform the reverse functionality, useexplode.

Q4). What is difference between include() and require() in PHP?

Answer:

PHP include() function causes the PHP parser to open the specified .php file and execute it before doing further processing. The included file acts as a normal PHP script. Hence, the output text is sent directly to the browser

An interesting point to note is that we can specify either a local file or remote file present on a remote location. (http://, file://, etc). In that case, PHP parser will first fetch the remote file and execute it.

On the other side, PHP require() function is identical to include() function, but there is a big difference between PHP include and PHP require functions. When a file is included using include() function and suppose that file is not present, the PHP script will continue execution, it will not stop. Meaning that it treats this as a warning.

Whereas when the file is included using require() function and file is not present, PHP would throw an error and exit from the PHP script. Awesome PHP Interview Questions for Experienced Developers.

Q5). What is a static variable in PHP and how to use them?

Answer:

The PHP static variable is a special kind of variable that can retail value between function calls.

Normally, the non-static variable lost its value after the control returns from the function. So, the static variable retains its value even after leaving the function.

PHP static variables are created using static keyword. The static variable is initialized only once.

Here, note that count is initialized to 0 only once. PHP Interview Questions for Experienced

Q6). Does PHP support Object-Oriented-Programming concepts?

The earlier releases of PHP were a purely procedural language where you could define functions and concepts OOPs, Classes, and Objects was not introduced. Awesome PHP Interview Questions for Experienced Developers.

PHP evolved over the years and now from PHP 4, it starts supporting the concept of OOPs (classes and objects)But, PHP is not pure and strong Object-Oriented programming language because of some limitations.

Q7). How to define a class in PHP and create objects?

A class in PHP is a logical abstraction of an object. It encapsulates the data and associated methods to access that data.

The data part is known as the properties of a class and functions that manipulate properties are called Methods.

And, an object is a variable of class type. So, in simple terms, a Class is just a definition of an object. PHP Interview Questions for Experienced

Q8). How to define a function in PHP? How to call the function in PHP?

Answer:

A function in PHP is a piece of code to perform a particular task. For example, user-defined sum() function to calculate the sum of two numbers, calculateSalary() to calculate the salary of an employee.

PHP functions help to organize the code that can be re-used later.

Use the function keyword to define a new user-defined function in PHP.

How to declare the function in PHP?

PHP function keyword followed by function-name is used to declare/define a function:

“boolean”“integer”“double” (for historical reasons “double” is returned in case of a float, and not simply “float”)“string”“array”“object”“resource”“resource (closed)” as of PHP 7.2.0“NULL”“unknown type”

PHP gettype() example<?php

$arData = array(1, 1., NULL, new stdClass, ‘foo’);

foreach ($arData as $value)

{echo gettype($value), “\n”;}

?>

Output

integerdoubleNULLobjectstring

Q14). How to delete a file in PHP?

Answer:

The PHP unlink() function can be used to permanently delete the given file form the system.

Q18). What is the use of $_REQUEST variables in PHP?

Answer:

$_REQUEST is a global variable in PHP used to retrieve user data after the HTML form submitted to the server. This is a superglobal variable means that it’s available in all PHP scripts in an application.

It is by default an associative array which holds the contents of $_POST and $_GET variables.

Q21). What is a permanent or persistent cookie in PHP?

Answer:

There are two types of Cookies in PHP:1. Temporary Cookie in PHPBy default, a temporary cookie is created and stored in the client’s browser memory. So, when the browser is closed, the temporary cookie will also be removed from the browser memory, that’s why its called temporary cookie.

2. Persistent Cookie in PHPA persistent cookie in PHP is stored in the client browser permanently. It retains the vale even after the client browser is closed. Persistent cookies are used to keep users long-term information.

Temporary cookies are more secure than persistent cookies. This is because persistent cookies are stored in a file that the user can open.

How to create a persistent cookie in PHPPHP setcookie() function is used to create a permanent cookie and send along with HTTP response to the user.

Note:Note that the value portion of the cookie will automatically be urlencoded when you send the cookie, and when it is received, it is automatically be decoded and assigned back to a variable by the same name as the cookie name.

Q22). What is the GD library in PHP?

Answer:

PHP GD library is a Graphics Drawing library in PHP which provides a rich set of functions to create, modify, customize and manipulate images in PHP applications.It supports JPG, PNG, GIF and more.

Q23). What is PDO in PHP?

Answer:

PDO stands for PHP Data Objects.

PHP PDO is an extension which provides a lightweight, simple, and flexible interface for interacting with the databases.

In simple terms, PDO is an abstract layer which provides a common interface between the developer and underlying database.

So, the same interface can be used to communicate with any type of database.

Q24). What are the traits in PHP and how to implement traits in PHP?

Answer:

Since PHP5.4.0 onwards, PHP has introduced the concept of PHP Traits for code reusability. PHP trait is similar to an abstract class in PHP that can be instantiated but more convenient than single inheritance.

It was introduced to counter some limitation of single inheritance in PHP.

Basically, traits are used to compose multiple objects into a single unit and provides a better interface than inheritance.

PHP trait example<?php trait ezcReflectionReturnInfo

{ function Fun1() { /*1*/ } function Fun2() { /*2*/ } }

Q25). What is a Composer in PHP? when to use it?

Answer:

Composer in PHP is a very powerful package manager tool. PHP composer is used to install, uninstall, update new packages.

To install Composer, you first need to download the installer file and send it to PHP.

The composer is very helpful for developers to manage third-party packages in PHP based projects.

Conclusion:

We hope this guide on PHP Interview Questions for Experienced must have helped to improve your existing PHP knowledge base. Ultimately, this guide will help you to boost your confidence level before sitting in the PHP Interview.